If your username and password was correct and invalid credentials message was displayed, then you are checking your Gmail too many times (Google recommends to check for new e-mails once every 10 minutes)
Solution: Clear your CAPTCHA for that account to access it via POP/IMAP.
Visit https://www.google.com/accounts/DisplayUnlockCaptcha
My commonly used Thunderbird Keyboard Shortcuts. //Dedicated to Laco ;)
N - Go to Next Unread Message
A - Archive Message
CTRL+N - Create new Message
CTRL+R - Reply to Message (sender only)
Ctrl+Shift+R - Reply to All (all recipients)
CTRL+ENTER - Send message
CTRL+K - Focus the quick search box
\ - Collapse All Threads
* - Expand All Threads
ESC-ESC - Focus the thread pane
ESC-M - Focus the message pane
Ctrl-Left/Right - Scroll the message from the thread pane
L - Hide/show the folder pane
G - Open a specific folder
S - Move the current message to a specific folder
B - Move the current message to a specific folder and go there
C - Copy the current message to a specific folder
Nostalgy introduces a notion of rule . A rule associates a folder to a message by looking for a substring of the From, To/Cc, or Subject headers (or a combination of them). A rule can be restricted to match messages only under a given server/folder. When a rule selects a folder for a given message, Nostalgy informs you in the status line. You can then use the Shift-S/Shift-C/Shift-G/Shift-B shortcuts to move/copy/go directly to this folder.
When typing in a header, it's possible to change easily the header to either "To:", "Cc:" or "Bcc:". To do so, you need to be at the beginning of the input box, and simply type "to ", "cc " or "bcc " (with the whitespace, without the quotes).
The ESC-ESC combination focuses the message body. The ESC-A combination opens the file attachment dialog.
Switch to new version of Thunderbird and install CustomizeHeaderToolbar Extension, then right click on header -> Customize -> Show -> Icons and add or remove items by dragging. ;)
Your Google Calendar ID for your primary calendar is just your email address, but for all other calendars the Calendar ID will be in the form of [ long string of characters]@group.calendar.google.com. You can get the Calendar ID by clicking the down arrow next to your calendar at calendar.google.com and selecting 'Calendar Settings'.